6 tablespoons water
2 tablespoons bread flour
For the rest:
1/4 cup whole milk
1 1/2 teaspoons active dry yeast
320 grams bread flour, plus up to 30 grams more
1 teaspoon salt
1/4 cup sugar
1/4 cup heavy whipping cream
1 tablespoon sweetened condensed milk or milk powder (optional)
2 eggs, 1 for the dough and 1 for the egg wash
2 tablespoons butter, softened
1 splash milk or water, for the egg wash
For the black sesame paste:
½ cup toasted black sesame seeds, finely ground
½ cup granulated sugar
½ cup unsalted butter, softened
In a small saucepan, whisk together 6 tablespoons of water and 2 tablespoons of bread flour until no lumps remain. Heat the mixture over medium-low heat, whisking constantly. It should thicken to a gel-like consistency after just a few minutes. As soon as lines appear in the mixture when stirred, remove it from the heat and transfer it to a small, clean bowl. Let cool to room temperature.
Next, heat the milk briefly to just above room temperature, about 110° F or lukewarm to the touch. Sprinkle the yeast over the milk and set it aside for 5 to 10 minutes for the yeast to activate.
In the meantime, whisk together 2 1/2 cups of the bread flour, salt, and sugar in a large bowl. In a smaller bowl or a measuring cup, whisk together the tangzhong, cream, condensed milk (or milk powder), and one egg.
When it’s ready, add the yeast mixture to the wet ingredients, and whisk gently, just to incorporate. Make a well in the dry ingredients and pour in all of the wet ingredients. Stir with a wooden spoon until the mixture forms a loose, shaggy dough, then switch to using your hands. Knead for 4 to 5 minutes, or until the dough forms a semi-smooth ball. The dough will be quite sticky — sprinkle the extra 1/4 cup flour, a tablespoon or so at a time, over the dough and your hands as you knead to keep it from sticking too much. I usually use at least 2 tablespoons and often up to the full amount, but you may not need it all.
Add the butter to the dough, one tablespoon at a time, kneading after each addition. Add the second tablespoon of butter only after the first has been evenly incorporated. The dough will be slippery and messy at this point, but just keep kneading and it should eventually form a soft and pliable dough that’s easy to work with. Knead for an additional 4 to 5 minutes, or until the dough becomes smooth and elastic.
Place the dough in a large bowl with plenty of room and cover the bowl with plastic wrap or a damp towel. Let rise for 1 to 2 hours, or until well doubled.
Once the dough is doubled gently deflate the dough and divide into 4 equal portions. Shape each piece into a ball and roll them out into an oval using a rolling pin on a well floured surface. Fold the right side (lengthwise) over to the middle and then fold the left side (lengthwise) over to the middle so both sides meet but are not overlapped. Roll the dough out into an oval again and then spread with black sesame paste. Starting from the edge of the short side, roll the dough up into a cylinder like you would roll up a sleeping bag.
Place each piece seam side down in the prepared loaf pan and repeat with the remaining dough. Cover and let rise for another hour or so. After about 40 minutes, preheat the oven to 350° F. When the dough seems ready, test it by pressing it gently with one finger; when the indentation bounces back slowly but remains visible, the dough is ready to bake.
Whisk your second egg with a splash of milk or water, and brush the egg wash over the dough. Bake for about 30 minutes, or until golden-brown on top. Internal temp should be 200 degrees F.
For the black sesame paste:
Finely grind the black sesame seeds in a spice grinder or small food processor. Add the sugar and softened butter. Pulse to make a paste. Transfer to a small bowl, cover, and set aside.
You can refrigerate this in advance. Before using, bring to room temperature to ensure it has a spreadable consistency.